In Python/sysmodule.c the function sys_update_path() uses wcscpy to copy data to a fixed size buffer. The input comes from an external source (argv[0]) and could theoretically be larger than the buffer.
Suggested solution:
Increase the buffer a bit:
wchar_t argv0copy[sizeof(wchar_t)* (MAXPATHLEN+1)];
and use wcsncpy:
wcsncpy(argv0copy, argv0, MAXPATHLEN);
argv0copy[MAXPATHLEN] = L'\0';
CID 486850